The invention relates to chemical delivery systems, and in particular to an apparatus for containing, purifying, and delivering a gaseous product that is sufficiently pure for use in the electronics industry, such as for semiconductor fabrication and processing. However, the invention is not limited to those applications and may have other uses, such as in commercial processes that use high purity gas from tanks or cylinders of compressed or liquefied gas.
Semiconductor manufacturers require high-purity gases and chemicals for production processes to avoid defects in the fabrication of semiconductor devices. Typical processing steps include using cleaning solvents for initial wafer preparation, wet etching, chemical vapor deposition, and the like. The presence of very minute amounts of impurities at any one step may result in contamination of the wafer, which may result in a reduction in semiconductor device yield or having to scrap the chip.
As semiconductor feature sizes continue to shrink, increasingly greater demands are placed on the required purity of the gases and chemicals used to produce semiconductor devices. As a means to increase yields, semiconductor fabrication facilities (xe2x80x9cfabsxe2x80x9d) commonly require process gases to meet particle specifications of less than 0.02 micron and metal specifications on the order of one part per billion or less. It is anticipated that industry standards will become more stringent in the future, as semiconductor feature sizes continue to shrink.
Electronic grades of process gases commonly have been supplied to semiconductor manufacturers in cylinders or tanks. However, as specifications regarding impurity concentrations have become more stringent, it has become more difficult to supply gases of sufficient purity for semiconductor processing. Even special preparation of the cylinders or containers by polishing and baking the inner surfaces fails to produce sufficient purity. Therefore, purifiers at the point of use often have been employed to remove contaminants and raise the purity of the gases on delivery.
Many prior art systems purify the gas after it exits the bulk container by using an external purifier. A disadvantage of this approach is that the piping between the bulk gas container and the external purifier is not protected in such systems. In addition, since the external purifier is required to withstand significant gas pressure, it can be very expensive.
Some gases are supplied in large, horizontal liquefied gas cylinders, such as xe2x80x9cYxe2x80x9d cylinders. Examples include HCl, Cl2, and SF6. Large external purifiers are required to consistently and reliably meet the purity requirements of the processes using these gases. In addition to being expensive, these purifiers require a sizeable footprint in the facility layout.
In addition, the piping between the cylinder and purifier is not protected from the deleterious effects of moisture corrosion when moisture is present in the gas. This is particularly significant because the high pressure portions of the piping system are the most vulnerable to corrosion, since the partial pressure of moisture is the greatest at this point in a distribution system.
In attempting to address the problem, various approaches have been taken with in-tank purifiers. Although in-tank purifiers designed to remove contaminants from compressed gases or liquefied gases by high-pressure cylinders have been long known, as shown in U.S. Pat. No. 1,821,549 (Hornor, et al.), problems remain and those prior art in-tank purifiers do not meet the current or future purity requirements of the electronics industry.
U.S. Pat. No. 5,409,526 (Zheng, et al.) discloses an apparatus for purifying gases delivered from vertical gas cylinders. The built-in purifier taught by Zheng, et al. works well for vertical cylinders. However, such a straight tube purifier cannot be used in horizontal liquefied gas cylinders, because the tube might become submerged below the liquid level, leading to unpredictable and potentially adverse results during product withdrawal.
U.S. Pat. No. 5,980,599 (Chris, et al.) discloses an in-tank purifier using a displacable purifier body. The arrangement of this purifier also is limited to use in vertical cylinders, and the purifier would have similar problems with horizontal liquefied gas cylinders as discussed above for the built-in purifier of Zheng, et al.
It is desired to have an apparatus for purifying a gaseous product delivered from a horizontal container, especially a gaseous product that may be used in the fabrication of semiconductor devices.
It is further desired to have a horizontal container containing a supply of a fluid delivering a gaseous product that meets stringent purity requirements, such as the requirements for semiconductor manufacturing processes.
It is still further desired to have a more reliable apparatus and method for delivering a high-purity gaseous product for use in the electronics industry, such as for semiconductor manufacturing processes.
It also is desired to have an apparatus and method for delivering high-purity gaseous products which overcome the difficulties and disadvantages of the prior art to provide better and more advantageous results.
The invention is an apparatus for purifying a gaseous product delivered from a substantially horizontal container containing a supply of a fluid. The invention also includes a substantially horizontal container for containing a supply of a fluid and delivering a gaseous product.
A first embodiment of the invention is an apparatus for purifying a gaseous product delivered from a substantially horizontal container adapted to contain a supply of a fluid. The container has a substantially horizontal axis, at least one inner wall, a first end, a second end opposite the first end, a port adjacent the first end, and an open interior for containing the fluid between the at least one inner wall and the first and second ends. At least part of the open interior is a vapor space. The apparatus includes an elongated hollow tube and a purifying medium disposed in at least a portion of the elongated hollow tube. The elongated hollow tube has a first opening, a second opening spaced apart from the first opening, and an internal axis between the first and second openings. The first opening is in fluid communication with the port and the second opening is in fluid communication with the vapor space. The portion of the internal axis adjacent the second opening is at an angle greater than zero degrees relative to the substantially horizontal longitudinal axis. The purifying medium is disposed between the first and second openings of the elongated hollow tube.
There are several variations of the first embodiment of the apparatus. In one variation, the gaseous product is used in the fabrication of a semiconductor device. In another variation, the fluid is selected from a group consisting of a compressed gas, a liquefied compressed gas, and a supercritical fluid. In yet another variation, the purifying medium comprises at least one layer of a material selected from a group consisting of at least one catalyst, at least one adsorbent, and at least one mixture thereof. In still another variation, the angle is about 45 degrees (45xc2x0).
There also are alternate embodiments of the apparatus. Several of these embodiments are similar to the first embodiment of the apparatus but include an additional element or feature. For example, a second embodiment of the apparatus includes a first filter disposed in the vapor space and in fluid communication with the second opening. A third embodiment of the apparatus includes a second filter adjacent the first opening and in fluid communication with the elongated hollow tube. A fourth embodiment of the apparatus includes control means in fluid communication with the port and adapted to control delivery of the gaseous product from the substantially horizontal container and delivery of the fluid to the substantially horizontal container.
A fifth embodiment is an apparatus for purifying a gaseous product to be used in the fabrication of a semiconductor device, the product being delivered from a substantially horizontal container having a substantially cylindrical shape adapted to contain a supply of a liquid. The container has a substantially horizontal longitudinal axis, at least one inner wall, a first end, a second end opposite the first end, a port adjacent the first end, and an open interior for containing the liquid between the at least one inner wall and the first and second ends. At least part of the open interior is a vapor space above a surface of the liquid. The apparatus includes at least five elements. The first element is an elongated hollow tube disposed in the open interior of the horizontal container. The elongated hollow tube has a first opening and a second opening spaced apart from the first opening. The first opening is in fluid communication with the port and the second opening is in fluid communication with the vapor space. A first portion of the tube proximate the opening is substantially parallel to the substantially horizontal longitudinal axis. A second portion of the tube distal the first opening is at an angle greater than zero degrees relative to the substantially horizontal axis. The second element is a purifying medium disposed in at least a portion of the elongated hollow tube between the first opening and the second opening. The purifying medium comprises at least one layer of a material selected from a group consisting of at least one catalyst, at least one adsorbent, and at least one mixture thereof. The third element is a first filter disposed in the vapor space and in fluid communication with the second opening. The fourth element is a second filter adjacent the first opening and in fluid communication with the elongated hollow tube. The fifth element is a control means in fluid communication with the port and adapted to control delivery of the gaseous product from the substantially horizontal container and delivery of a source of the liquid to the substantially horizontal container. (The source of the liquid may be gaseous, liquid, a two-phase fluid, or any combination thereof.)
Another aspect of the invention is a substantially horizontal container for containing a supply of a fluid and delivering a gaseous product. A first embodiment of the container has a built-in purifier for purifying the gaseous product delivered from the container. The container has a substantially horizontal longitudinal axis, at least one inner wall, a first end, a second end opposite the first end, a port adjacent the first end, and an open interior for containing the fluid between the at least one inner wall and the first and second ends. At least part of the open interior is a vapor space. The built-in purifier includes an elongated hollow tube disposed in the open interior of the horizontal container and a purifying medium disposed in at least a portion of the elongated hollow tube. The elongated hollow tube has a first opening, a second opening spaced apart from the first opening, and an internal axis between the first and second openings. The first opening is in fluid communication with the port and the second opening is in fluid communication with the vapor space. A portion of the internal axis adjacent the second opening is at an angle greater than zero degrees relative to the substantially horizontal longitudinal axis. The purifying medium is disposed between the first and second openings of the elongated hollow tube.
There are several variations of the first embodiment of the container. In one variation, the gaseous product is used in the fabrication of a semiconductor device. In another variation, the fluid is selected from a group consisting of a compressed gas, a liquefied compressed gas, and a supercritical fluid. In yet another variation, the purifying medium includes at least one layer of a material selected from a group consisting of at least one catalyst, at least one adsorbent, and at least one mixture thereof. In still another variation, the angle is at about 45 degrees (45xc2x0). In yet still another variation, at least a portion of the fluid is a liquid having a substantially horizontal liquid surface, and the container has a visually observable index designating a desired positioning of the container in a predetermined desired position. When the container is positioned approximately in the predetermined desired position, the second opening is located in the vapor space. Preferably, the desired positioning provides for a perpendicular distance between the liquid surface and the second opening at or substantially near a maximum perpendicular distance obtainable between the liquid surface and the second opening.
There also are several alternate embodiments of the container. Several of these embodiments are similar to the first embodiment of the container but include at least one additional element or feature. For example, a second embodiment of the container includes a first filter disposed in the vapor space and in fluid communication with the second opening. A third embodiment of the container includes a second filter adjacent the first opening and in fluid communication with the elongated hollow tube. A fourth embodiment of the container includes control means in fluid communication with the port and adapted to control delivery of the gaseous product from the substantially horizontal container and delivery of the fluid to the substantially horizontal container.
A fifth embodiment is a substantially horizontal container having a substantially cylindrical shape for containing a supply of a liquid having a substantially horizontal liquid surface and for delivering a gaseous product to be used in the fabrication of a semiconductor device. The container has a built-in purifier for purifying the gaseous product delivered from the container and having a substantially horizontal longitudinal axis, an inner wall, an outer wall, a first end, a second end opposite the first end, a port adjacent the first end, and a open interior for containing the liquid between the inner wall and the first and second ends. At least part of the open interior is a vapor space above the liquid surface. The built-in purifier includes at least five elements. The first element is an elongated hollow tube disposed in the open interior of the horizontal container. The elongated hollow tube has a first opening, a second opening spaced apart from the first opening, and an internal axis between the first and second openings. The first opening is in fluid communication with the port and the second opening is in fluid communication with the vapor space. A first portion of the tube proximate the first opening is substantially parallel to the substantially horizontal longitudinal axis. A second portion of the tube distal the fist opening is at an angle greater than zero degrees relative to the substantially horizontal longitudinal axis. The second element is a purifying medium disposed in at least a portion of the elongated hollow tube between the first opening and the second opening. The purifying medium includes at least one layer of a material selected from a group consisting of at least one catalyst, at least one adsorbent, and at least one mixture thereof. The third element is a first filter disposed in the vapor space and in fluid communication with the second opening. The fourth element is a second filter adjacent the first opening and in fluid communication with the elongated hollow tube. The fifth element is a control means in fluid communication with the port and adapted to control delivery of the gaseous product from the substantially horizontal container and delivery of a source of the liquid to the substantially horizontal container. (The source of the liquid may be gaseous, liquid, a two-phase fluid, or any combination thereof.)
In a variation of the fifth embodiment of the container, the container has a visually observable index designating a desired positioning of the container in a predetermined desired position. When the container is positioned approximately in the predetermined desired position, the second opening is located in the vapor space. Preferably, the desired positioning provides for a perpendicular distance between the liquid surface and the second opening at or substantially near a maximum perpendicular distance obtainable between the liquid surface and the second opening.